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KVM: VMX: update PFEC_MASK/PFEC_MATCH together with PF intercept 

The PFEC_MASK and PFEC_MATCH fields in the VMCS reverse the meaning of
the #PF intercept bit in the exception bitmap when they do not match.
This means that, if PFEC_MASK and/or PFEC_MATCH are set, the
hypervisor can get a vmexit for #PF exceptions even when the
corresponding bit is clear in the exception bitmap.

This is unexpected and is promptly detected by a WARN_ON_ONCE.
To fix it, reset PFEC_MASK and PFEC_MATCH when the #PF intercept
is disabled (as is common with enable_ept && !allow_smaller_maxphyaddr).

Reported-by: Qian Cai <cai@redhat.com>>
Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2020-09-29 08:31:32 -04:00
parent 4bb05f3048
commit b502e6ecdc
1 changed files with 12 additions and 10 deletions
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22
arch/x86/kvm/vmx/vmx.c
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@ -794,6 +794,18 @@ void update_exception_bitmap(struct kvm_vcpu *vcpu)
*/
if (is_guest_mode(vcpu))
eb |= get_vmcs12(vcpu)->exception_bitmap;
else {
/*
* If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched
* between guest and host. In that case we only care about present
* faults. For vmcs02, however, PFEC_MASK and PFEC_MATCH are set in
* prepare_vmcs02_rare.
*/
bool selective_pf_trap = enable_ept && (eb & (1u << PF_VECTOR));
int mask = selective_pf_trap ? PFERR_PRESENT_MASK : 0;
vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, mask);
vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, mask);
}
vmcs_write32(EXCEPTION_BITMAP, eb);
}
@ -4355,16 +4367,6 @@ static void init_vmcs(struct vcpu_vmx *vmx)
vmx->pt_desc.guest.output_mask = 0x7F;
vmcs_write64(GUEST_IA32_RTIT_CTL, 0);
}
/*
* If EPT is enabled, #PF is only trapped if MAXPHYADDR is mismatched
* between guest and host. In that case we only care about present
* faults.
*/
if (enable_ept) {
vmcs_write32(PAGE_FAULT_ERROR_CODE_MASK, PFERR_PRESENT_MASK);
vmcs_write32(PAGE_FAULT_ERROR_CODE_MATCH, PFERR_PRESENT_MASK);
}
}
static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)